1. Field of the Invention
This invention relates to a spray generator for generating a spray of droplets from the interaction of opposed jets of fluid.
2. Background of the Related Art
Spray generators of this type are known and are used in a variety of applications, e.g. for providing an intimate contact between a gas and a liquid in gas scrubbers, distillation columns, steam and air stripping columns and other mass transfer devices.
GB949954 describes a spray-producing apparatus in which liquid is fed into the opposite ends of a duct having an opening, or slot, in its wall. The two flows of liquid collide with each other and generate a spray of droplets that issue from the slot. The liquid fed to the two ends of the duct is subject to pulsating pressure of different phases. By varying the phase relationship of the two flows, the angle of spread of the spray can be controlled. This apparatus is described as being of use in the brewing industry to spray wort over a filter bed.
U.S. Pat. No. 4,002,293 describes an apparatus for producing liquid sprays, e.g. for fountains or in apparatus such as a dishwasher, in which two jets of pressured streams of liquid are directed at each other along a common axis. Nozzles of different configurations can be used to vary the shape of the spray pattern produced and the sprays may be varied in a regular or random manner by interrupting or varying the pressures of the streams.
EP0331343 and EP0642836 describe a spray generator for use in a gas absorption process. A pair of opposed nozzles are located axially within a vortex chamber and fluid issuing from the nozzles interacts to produce a spray of drops. A uniform cyclic disturbance can be imposed on the flows of liquid to the nozzles to produce a reduction in the droplet size spectrum or an irregular variation may be used to generate a spray pattern which changes in an irregular manner.
The present invention aims to improve upon this prior art and overcome or reduce some of the problems associated therewith.
According to a first aspect of the invention, there is provided a spray generator that generates a spray of droplets by an interaction of opposed jets of fluid, the generator comprising: a rigid central member defining a central axis, and fluid passageways formed in a block or blocks of material leading to two or more pairs of opposed fluid outlets, the outlets of each pair being separated from each other and arranged to generate opposed jets of fluid along an axis parallel to said central axis and the pairs being equi-angularly spaced about said central axis, the outlets of each pair being maintained in axial alignment with each other and at a predetermined axial spacing from each other by a rigid connection between the central member and the said block or blocks of material, the arrangement being such that, in use, the two or more pairs of outlets together generate a spray of droplets extending 360 degrees about the central axis.
According to a second aspect of the invention there is provided a spray generator for generating a spray of droplets by the interaction of opposed jets of fluid, the generator having a nozzle component which comprises a central member defining a central axis and at least two pairs of opposed fluid outlet, the outlets of each pair being spaced from each other and arranged to provide opposed jets of fluid along an axis parallel to the central axis, the pairs of opposed fluid outlets being equi-angularly spaced around the central axis, and being rigidly connected to the central member to maintain the outlets of each pair in axial alignment with each other and at a predetermined spacing from each other.
According to another aspect of the invention there is provided a vortex chamber or a plurality of vortex chambers each having a spray generator as detailed above mounted therein.
The invention thus overcomes problems associated with the prior art in maintaining the fluid outlets in precise alignment with each other (so they are co-axial) and maintaining them at a pre-set distance from each other, whilst being able to generate a 360 degree spray. A slight misalignment between opposed fluid outlets can skew the spray pattern produced or prevent the desired spray pattern being generated. This is of particular concern when high pressure fluid flows are used, e.g. in a vortex type gas/liquid contactor, as they are sensitive to very small misalignment and the high pressures used can cause the apparatus to distort. The separation between the outlets is also critical to the correct functioning of the generator, the separation typically being equal to the diameter of the outlets. This problem has, in the past, been addressed by making the nozzles and the apparatus on which the respective nozzles are mounted of substantial, rigid construction. However, this leads to an undesirable increase in the size and cost of the apparatus and, particularly with large apparatus, it is still difficult to achieve the required accuracy of alignment and spacing of the nozzles, especially in a situation involving high temperatures and hence significant thermal expansion. To overcome this, nozzles such as those described in EP0331343 and EP0642836 have, in practice, been contained within a support structure such as a cage with two or more rods as tie-bars to hold the nozzles in alignment. These tie bars are mounted around the outer circumference of the nozzles and thus obstruct a portion of the spray issuing from between the nozzles. Also, when spray hits the bars, it is shattered into much smaller droplets which is undesirable in some applications as such small droplets are more difficult to remove from the gas flow before the gas leaves the scrubber.
As indicated above, the present invention uses two or more pairs of outlets and has a central member to maintain the axial alignment and spacing of the outlets of the respective pairs.
Preferred and optional features of the invention will be apparent from the following description and from the subsidiary claims of the specification.